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Boyle, Robert, 1627-1691

"Experiments and Considerations Touching Colours (1664)"


Eighthly, But if it were Rubb'd upon a convenient Body for a pretty while,
and Briskly enough, I found the Light would be for some moments much more
considerable, almost like the Light of a Glow-worm, insomuch after I ceased
Rubbing, I could with the Chaf'd stone exhibit a little Luminous Circle,
like that, but not so bright as that which Children make by moving a stick
Fir'd at the end, and in this case it would continue Visible about seven or
eight times as long as I had been in Rubbing it.
Ninthly, I found that holding it a while near[39] the Flame of a Candle,
(from which yet I was carefull to avert my Eyes) and being immediately
remov'd into the Dark, it disclosed some faint Glimmering, but inferiour to
that, it was wont to acquire by Rubbing. And afterward holding it near a
Fire that had but little Flame, I found the Stone to be rather less than
more excited, than it had been by the Candle.
[39] IX. _We durst not hold it in the Flame of a Candle, no more than put
it into a naked Fire; For fear too Violent a Heat (which has been
observ'd to spoil many other precious Stones) should vitiate and impair a
Jewel, that was but borrow'd, and was suppos'd to be the only one of its
Kind.


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